A river basin is an area of land drained by a river and its tributaries. River basins have typical features, these include:
Tributaries - smaller rivers flowing into a larger river.
A Watershed - an area of highland surrounding the river basin.
A confluence - where a river joins another river.
Source - the start of a river.
Mouth - Where a river meets a lake, the sea or an ocean.
The diagram below shows these features.